1. Field of the Invention
The present invention relates to a retractable lens capable of a high variable magnification.
2. Description of the Related Art
Recently, there has been demand for further size reductions of compact devices that capture images, such as digital still cameras and home video cameras. In response to this demand, the length of lens systems mounted on compact image capturing devices has been reduced. In particular, lens systems mounted on digital still cameras, in addition to having a reduced length, are given wider angles and improved performance to accommodate higher pixilation of imaging devices (see, for example, Japanese Patent Application Laid-Open Publication Nos. 2005-338740, 2006-023530, 2006-023531, 2006-171055, and 2006-308649).
To implement shorter lens systems, especially, a zoom lens at the time of retraction (the most shortened state of a zoom lens, i.e., the state of a zoom lens at the time of power-off of the device to which the zoom lens is mounted), the lengths of lens groups making up the zoom lens are reduced along the optical axis in addition to a reduction of the space between a first lens group and a second lens group, and the space between the second lens group and a third lens group. In conventional zoom lenses, such as those disclosed in the references cited above, vertical magnification is reduced with respect to an image plane of the space in the third lens group to meet such requirements. However, although reductions in length may be achieved, this technique is problematic in that it is difficult to widen the angle of the zoom lens.
A technique of displacing, from the optical axis, a portion of optical members making up a zoom lens at the time of retraction is effective in reducing the thickness of a zoom lens. However, although reductions in thickness may be achieved, if an optical vibration-proof function, etc., is incorporated into the zoom lens, it is difficult to widen the angle.